7-Zip is a free file compression program that also allows you to encrypt and password protect the files you compress.
Can I use 7-Zip at home?
Yes, 7-Zip is free software. You can use it on any computer. You don't need to register or pay for 7-Zip.
How can I make 7-zip open ZIP files in Windows 7?
You must run 7-Zip File Manager in administrator mode. Right-click the icon of 7-Zip File Manager, and then click Run as administrator. Go to the “tools” menu, at the top of the program, and select “options”. There you can change file associations and some other options. We recommend clicking the “Select All” button under file associations so 7zip will open all archives.
Why can't 7-Zip open some ZIP archives?
In 99% of these cases it means that the archive contains incorrect headers. Other ZIP programs can open some archives with incorrect headers, since these programs just ignore errors. Contact the person who sent you the ZIP file and ask them to remake it – perhaps in 7zip.